WO 92/05828 discloses a wire-form suture which comprises an open wire ring, the ends of which have been arranged to overlap. The wire-formed ring can be fully or partially straightened, one end sharpened and the whole device driven through adjoining tissues. The wire has a spring or shape memory characteristic which causes it to re-form into a ring shape when in place thereby drawing together the tissues.
An improvement to this design is disclosed in WO 00/07506 (in the name of the present applicant—published after the priority date of the present application), in which a pair of joined wires have a shape memory which causes them to form an ‘H’ shape upon deployment. This shape has the advantage of symmetry which ensures that the orientation of the device remains stable after implementation. It also has the advantage that the overall width of the device increases after implantation. This reduces the possibility of the device's pulling out from its implantation site. Both of these advantages are particularly important in the critical application of intra-arterial implantation.
A requirement of the design disclosed in WO 00/07506 is that the part of the device where the wires are attached to each other is intended to lie within the wall of the artery and the graft with the divided parts of the device projecting beyond the artery walls and graft on both the lumenal and the visceral sides. A consequence of this requirement is that the paired wires must remain in contact with each other along their lengths while they pass through the artery and graft. If they do not, then the device may not pass fully through the structures or the device may remove a core of material (due to its increased width). This constrains the design of an appropriate delivery system and can increase the risk of misplacement of the device. Such misplacement could have serious consequences for a patient.